Fix LoadComponentAsync calls potentially occuring after beatmap wedge disposal
Fix LoadComponentAsync calls potentially occuring after beatmap wedge disposal

As seen in https://ci.appveyor.com/project/peppy/osu/builds/36109658/tests.

Also adds cancellation logic for good measure.

ppy/osu,NeoAdonis/osu,smoogipoo/osu,smoogipoo/osu,smoogipooo/osu,UselessToucan/osu,smoogipoo/osu,NeoAdonis/osu,peppy/osu-new,ppy/osu,ppy/osu,UselessToucan/osu,peppy/osu,peppy/osu,peppy/osu,UselessToucan/osu,NeoAdonis/osu